The proposed work consists of an ultrastructural study of myoneural and synaptic junctions in various animals. Examples of such junctions will be surveyed by means of transmission electron microscopy with the help of staining and preparative techniques designed to reveal details of membrane specializations. Equivalent studies will be carried out on central nervous system specimens. Comparable structures will be examined in a variety of junctions in order to distinguish essential from accidental structural components and to correlate structural differences with physiological differences. In addition experimental modification of the junctions will be carried out in order to determine the functions of specific structural elements and to reveal underlying structural details not visible in standard preparations.